【Servlet】Cookie应用：显示上次访问页面时间

怼烎@ 2022-06-15 08:17 108阅读 0赞

\#Q题目

**要求：**

显示上次访问页面时间，并添加清除Cookie功能

**如下图：**

![这里写图片描述][658811a3c63427574a73627c8e6c4fd8.png]

![这里写图片描述][f9e765741ce029e93c0e681a8d2754ae.png]

**清除Cookie**

![这里写图片描述][a8c5ca665610ae597e8a1ca161026db5.png]

--------------------

\#A 代码

**实现Cookie显示上次访问时间**

package com.tcb.cookie;
    
    import java.io.IOException;
    import java.io.PrintWriter;
    import java.util.Date;
    
    import javax.servlet.ServletException;
    import javax.servlet.http.Cookie;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    /**
     *说明：
     *1.该方式将时间直接以long类型存进Cookie
     *2.从Cookie中取出值后，需要先做日期格式化，才能展示
     *
     *优点：避免某些电脑浏览器因为Cookie值存储长短限制不能显示上次访问时间
     *
     *比如：“2017-05-04 20:33:22”,日期转为该格式后，不能存进Cookie中，因为Cookie长度限制
     *	 但直接以--时间戳（long类型）--的方式，可以直接存进Cookie
     */
    public class CookieServlet01 extends HttpServlet {
    	private static final long serialVersionUID = 1L;
           
        public CookieServlet01() {
            super();
        }
    
    	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		//编码格式
    		response.setContentType("text/html;charset=utf-8");
    		PrintWriter writer=response.getWriter();
    		
    		writer.write("上次访问时间：");
    		
    		Cookie[] cookies=request.getCookies();
    		if(cookies!=null){
    			//遍历cookies，取出lastAccessTime这个cookie
    			for (int i = 0; i < cookies.length; i++) {
    				Cookie c=cookies[i];
    				if("lastAccessTime".equals(c.getName())){
    					//取值上次访问时间，并显示出来
    					String time=c.getValue();
    					time=new Date(Long.parseLong(time)).toLocaleString();
    					writer.write(String.valueOf(time));
    				}
    			}
    		}
    		
    		writer.write("<a href="+request.getContextPath()+"/ClearCookieServlet>清除Cookie</a>");
    		
    		//获取当前时间，并存储到Cookie中
    		Long currentTime=System.currentTimeMillis();
    		Cookie cookie=new Cookie("lastAccessTime", currentTime.toString());
    		cookie.setMaxAge(5*60);//设置Cookie有效时间，5min内关闭再打开浏览器Cookie会一直存在
    		response.addCookie(cookie);
    		
    	}
    
    	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		// TODO Auto-generated method stub
    		doGet(request, response);
    	}
    
    }

**清除Cookie**

package com.tcb.cookie;
    
    import java.io.IOException;
    import javax.servlet.ServletException;
    import javax.servlet.http.Cookie;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    /**
     * 说明：
     *      清楚Cookie
     */
    public class ClearCookieServlet extends HttpServlet {
    	private static final long serialVersionUID = 1L;
           
        public ClearCookieServlet() {
            super();
        }
    
    	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		//清除cookie
    		
    		//清除cookie时，完全没必要先将cookie遍历出来，再去清除cookie，尽管下面的方法可以实现清除cookie
    		//我们可以根据cookie的特性，名字相同的cookie，后面设置的值会覆盖前面的值
    		/*Cookie[] cookies=request.getCookies();
    		if(cookies!=null){
    			for (Cookie cookie : cookies) {
    				if("lastAccessTime".equals(cookie.getName())){
    					cookie.setMaxAge(0);
    					response.addCookie(cookie);
    				}
    			}
    		}*/
    		
    		
    		//便捷做法
    		Cookie cookie=new Cookie("lastAccessTime", "");
    		cookie.setMaxAge(0);
    		response.addCookie(cookie);
    		
    	}
    
    	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		doGet(request, response);
    	}
    
    }

[658811a3c63427574a73627c8e6c4fd8.png]: /images/20220615/43181123f0e945eb82e6506b4441acba.png
[f9e765741ce029e93c0e681a8d2754ae.png]: /images/20220615/7850378412794882ba426d99f7608665.png
[a8c5ca665610ae597e8a1ca161026db5.png]: /images/20220615/ada0fb2a6d434578bc4c44b3b72f5018.png